1. Technical Field
The present invention relates to a discharge position adjusting method in which a droplet ejecting apparatus is used and to a droplet ejecting apparatus that employs the discharge position adjusting method to adjust the positions of dots to be created.
2. Related Art
Ink jet printers are a known example of droplet ejecting apparatuses. Such ink jet printers eject liquid droplets (ink droplets) onto various print media, including a paper sheet or a film, thereby printing or recording images thereon. Some ink jet printers perform a dot creating operation and a transport operation; in the dot creating operation, the head ejects ink droplets onto a print medium through a plurality of nozzles formed in the head while moving over or scanning the print medium in scanning directions, and in the transport operation, the print medium is moved or transported in a transport direction intersecting the scanning directions. Alternately repeating these dot creating and transport operations creates dots (dot rows) arranged in the scanning directions, creating an image on the print medium.
In order for ink jet printers, as described above, to create images with higher resolutions, finer nozzles in the heads tend to be arrayed at higher densities. With this tendency, print time typically increases, but some ink jet printers reduces an increase in print time by performing bidirectional printing; in bidirectional printing, a head creates dots when moving not only in a first scanning direction, which is one of the scanning directions, but also in a second scanning direction, which is opposite to the first direction. This bidirectional printing involves a highly precise adjustment of the relative position of respective dots to be created by the movements in the first and second scanning directions. This adjustment is referred to as “bid adjustment”. For example, JP-A-2003-266700 discloses a method of adjusting the positions of dots to be created, in which a variable dot printer that selectively ejects ink droplets of different sizes can perform the bid adjustment effectively.
In the disclosed method, bid adjustment needs to be performed head by head. So, if an ink jet printer that supports high-speed printing with multiple heads employs this method, the adjusting time may disadvantageously increase.